I take it that you mean catapult. In my (much) younger days we would only use a yew tree. the new branches form a nearly perfect 'Y'. That brings back some memories!
As a child I found the best wood in the US for the "Y" of the slingshot was hickory. However, I also found that a "U" shape cut with a jig-saw from 3/4" plywood to actually be the best. (With a handle of course). We used real rubber (called live rubber) from old inner tubes. Unfortunately, if one could even find such a tube today, it would be synthetic rubber, and not as elastic. Also used "tongues" from old shoes for the leather to carry the missle. Luck...!